The Official Pokemon website has finally revealed Giratina to North America. Coming exclusively to Nintendo DS on March 22nd, 2009, Pokemon Platinum Version introduces players to a new world to explore in the Sinnoh region: the Distortion World. While in the Distortion World, Giratina appears in its Origin Forme. When Giratina is outside the Distortion World, it appears in its Altered Forme.

Giratina Origin Forme: Category: Renegade Pokémon Type: Ghost/Dragon Ability: Levitate Height: 22'08" Weight: 649 Kg. (1433.0 lbs.)	Giratina Altered Forme: Category: Renegade Pokémon Type: Ghost/Dragon Ability: Pressure Height: 14'09" Weight: 750 Kg. (1653.5 lbs.)

You can view more information about Giratina by visiting the Dex.

Source: Pokemon.com